Problem: $ B = \left[\begin{array}{rrr}2 & 0 & 2 \\ 1 & 1 & 0 \\ 1 & 2 & 0\end{array}\right]$ What is $ B^{-1}$ ?
Solution: $ = \left[\begin{array}{rrr}0 & 2 & -1 \\ 0 & -1 & 1 \\ \frac{1}{2} & -2 & 1\end{array}\right]$